Combined Pressures and Climate Change Impacts on the Victorian Water System and Possible Responses

The impact of various climate change scenarios has been modelled on the water system of all the river basins across Victoria. Importantly, this analysis has been undertaken in combination with calculations of scenarios of Victorian demography, land-use and electricity generation. We employ a detailed physical account of these sectors using the Victorian Regional Stocks and Flows Framework (VRSFF). The results from the collection of scenarios in VRSFF show the significant impact that some climate scenarios may have on the water system. For example, if predictions of high climate change eventuate and major dam levels are maintained to support urban and rural water use, then our work shows that many of the 29 major river systems in Victoria will be significantly stressed, some dropping to less than 1/3 of their usual flow by mid to late this century. Factoring in possible yearly variations in climate means these river systems, such as the Thomson River and the Murray River entering the neighbouring state of South Australia, may intermittently stop flowing. We also explore potential climate change mitigation and adaptation options, which may also have negative impacts on water security but may be preferable to the alternative of not mitigating. In one scenario, reducing CO2 emissions from electricity generations to 50% of 1990 levels (i.e., not quite reaching a 60-90% target) by 2050 requires per capita consumption rates of goods and energy to be decreased from about 2.0% per year to 0.4%, while also increasing brown coal station efficiency by 25% and replacing most brown coal stations with low or near-zero emission technology, such as biomass, wind, and gas. This scenario produces the lower curve in Figure 1. This analysis clearly indicates the importance of combining technological options with reduced consumption for achieving proposed reductions in greenhouse emissions to avoid dangerous climate change. It also indicates the substantial extent of the change required, especially in terms of avoiding a "rebound" effect if energy end-use efficiencies are proposed as a means of reducing consumption. [GRAPHICS] .